Method and apparatus for phonation analysis lending to valid truth/lie decisions by spectral energy region comparison

ABSTRACT

A method and apparatus for indicating emotional stress in speech by normalizing the ratio of peak amplitude signals in two or more frequency regions of a single response. Normalization is achieved by comparing all subsequent ratios with a selected stored ratio of the same speaker.

Fuller [4 Dec. 17, 1974 SPECTRAL ENERGY REGION COMPARISON OTHERPUBLICATIONS Philip Lieberman, Some Acoustic Correlates of Word Stressin American English, J.A.S.A. 1960, pp. 451-54.

7 Inventor: Fred H Fuller, 4450 S Park s Lieberman & Michaels, SomeAspects Of Fundamen- Rockville Md 20014 tal Frequency & EnvelopeAmplitude as Related to the Emotional Content of Speech, J.A.S.A. 1962,pp. [22] Filed: Dec. 1, 1972 922 27 PP N031 311,391 Medical Electronics,Electronics, 6/1966, p. 40.

U-S. SA, Primary Examiner .David Stewart Int. Cl. I Anoyney Agent orFirm Fide]man wolffe Leitne [58] Field of Searchl79/l SA, 1 SB, 1 VS,15.55 R, & Hiney l79/l5.55 T, 1 SP; 128/206; 35/21 [56] References Cited[5 7] ABSTRACT UNITED STATES PATENTS A method and apparatus forindicating emotional 21181265 11/1939 Dudley 79/1 VS stress in speech bynormalizing the ratio of peak am- 3,238.303 3/1966 Dersch l79/l SAplitude Signals in two or more frequency regions of a 3,509,280 4/l970Jones 179/1 SB l N I. d b 3,588,363 6/1971 Herscher 179 1 sA m 8response ac y P 3,679 830 M972 Uffelman 179 SA mg all subsequent rat1oswIth a selected stored who of 3.752929 8/1973 Fletcher I79/I 5A the Samep FOREIGN PATENTS OR APPLICATIONS 9 Claims, 10 Drawing Figures 1,113,2255/1968 Great Britain 179/1 SA I6 20 24 AMPLIFIER A ND PASS EA DETEFILTER RECTF'ER I IX TER :NDK HOLDCTOR 4 l 48 CDV QLTMETER 44 I- RATIO467 TAKING MICROPHONE cIRcuIT 32A RATIo TAKING so mom 0 7 2 34 58 p30RECORDER SWITCH SWITCH coNTRoL l coNTRoL BAND PAss LOW PASS PEAKDETECTOR & FILTER RECT'F'ER FILTER AND HOLD AMPLIFIER PATENTEBUEE 1 H9741855,41?

PROB. 0 ACCURATE ASSESSMENT NONSTRESSFUL NONSTRESSFUL I T l .2 .6 T0 |.4L6 2.2

RATIO VALUES PROB. OF ACCURATE ASSESSMENT 74 6 STRESSFUL NONSTRESSFUL ,5I I I l l NORMALIZED RAT lo VALUES- METHOD AND APPARATUS FOR PHONATIONANALYSIS LENDING TO VALID TRUTH/LIE DECISIONS BY SPECTRAL ENERGY REGIONCOMPARISON BACKGROUND OF THE INVENTION The present invention relatesgenerally to voice signal analysis systems and more specifically to amethod and apparatus for detecting emotional stress within a voicepattern. The presence of an emotional state will be used to determinethe truthfulness of a response to questions asked by a skilledinterrogator.

DESCRIPTION OF THE PRIOR ART It has long been known that the voice maybe, and often is, used to convey the emotions of the speaker. Theemotional state of the speaker produces readily observable variation inthe measurable parameters of the voice.

Speech is the acoustic energy response of: a) the voluntary motions ofthe vocal cords and the vocal tract which consists of the throat, thenose, the mouth, the tongue, the lips and the pharynx, and b) theresonances of the various openings and cavities of the human head. Theprimary source of speech energy is excess air under pressure, containedin the lungs. This air pressure is allowed to flow out of the mouth andnose under muscular control which produces modulation. This flow iscontrolled or modulated by the human speaker in a variety of ways.

The major source of modulation is the vibration of the vocal cords. Thisvibration produces the major component of the voiced speech sounds, suchas those required when pronouncing the vowel sounds in a normal manner.These voiced sounds, formed by the buzzing action of the vocal cords,contrast to the voiceless sounds such as the letter s or the letter fproduced by the nose, tongue, and lips. This action of voicing is knownas phonation.

The basic buzz or pitch frequency, which establishes phonation, isdifferent for men and women. The vocal cords of a typical adultmale-vibrate or buzz at a frequency of about lHz, whereas for women thisbasic rate is approximately an octave higher, near 250Hz.

The basic pitch pulses of phonation contain many harmonics and overtonesof the fundamental rate in both men and women.

The vocal cords are capable of a variety of shapes and motions. Duringthe process of simple breathing, they are involuntarily held open andduring phonation, they are brought together. As air is expelled from thelungs, at the onset of phonation, the vocal cords vibrate back andforth, alternately closing and opening. Current physiologicalauthorities hold that the muscular tension and the effective mass of thecords is varied by the learned muscular action. These changes stronglyinfluence the oscillating or vibrating system.

Certain physiologists consider that phonation is established by orgoverned by two different structures in the pharynx, i.e. the vocal cordmuscles and a mucous membrane called the conus elasticus. These twostructures are acoustically coupled together at a mutual edge, withinthe pharynx and cooperate to produce two different modes of vibration.

In one mode, which seems to be an emotionally stable or non-stressfultimbre of voice, the conus elasticus and the vocal cord muscle vibrateas a unit in synchronism. Phonation in this mode sounds soft or mellowand few overtones are present.

In the second mode, a pitch cycle begins with a subglottal closure ofthe conus elasticus. This membrane is forced upward toward the couplededge of the vocal cord muscle in a wave-like fashion, by air pressurebeing expelled from the lungs. When the closure reaches the couplededge, a small puff of air explosively" occurs, giving rise to the openphase of vocal cord motion. After the explosive puff of air has beenreleased, the subglottal closure is pulled shut by a suction whichresults from the aspiration of air through the glottis. Shortly afterthis,'the vocal cord muscles also close. Thus in this mode, the twomasses tend to vibrate in opposite phase. The result is a relativelylong closed time alternated with short sharp air pulses which mayproduce numerous overtones and harmonics.

The balance of respiratory tract and the nasal and cranial cavities giverise to a variety of resonances, known as formants in the physiology ofspeech. The lowest frequency formant can be approximately identifiedwith the pharyngeal cavity, resonating as a closed pipe. The secondformant arises in the mouth cavity. The third formant is oftenconsidered related to the secondresonance of the pharyngeal cavity. Themodes of the higher order formants are too complex to be very simplyidentified. The frequency of the various formants vary greatly with theproduction of the various voiced sounds.

One of the acoustic correlates of emotional involvement transmittedthrough human speech is a measure of the normalized but relative peakenergy at low and high frequencies in voiced phonation. Statistical datareveals that the normalized ratio between peak input signal values,measured within specified frequency ranges, corresponds in a significantmanner to the degree of emotional stress during the assessed phonation.Other parameters through to be related to the emotional transmission ofinformation include: Phonetic Content, Gross Changes In FundamentalFrequency, the Speech Envelope Amplitude and the Fine Structure of theFundamental Pitch Frequency. This latter parameter is discussed in mycopending patent application, Ser. No. 31 1,392. These parameters allcontribute to the conveyance of emotion or a stressful conditionexisting in the speaker.

Speech analysis and the equipment for accomplishing the same has beendeveloped for a variety of loosely related purposes. One of the primaryconcerns is the transmission of speech with a high order ofintelligibility and presence over a very reduced bandwidth. Theapplicability of this particular art becomes obvious in civil andmilitary communications. Other fields in which speech analysis equipmentare used are the voice operated printing or recording device,such as atypewriter and systems, equipment and devices that are commanded andcontrolled by the spoken word or phrase. While these activities areinteresting and valuable in themselves, they do not relate to thedetection of emotional content of a speech wave nor its use to determinethe veracity of the speaker.

SUMMARY OF THE INVENTION The present invention determines the amount ofemotional stress in the voice of a person under interrogation bycomparing the peak amplitude in two different frequency ranges. The peakamplitudes in a l50-300I-Iz and a 600-1200I-Iz frequency band aredetected and held after separation by band-pass filters, rectifying andsmoothing. The ratio of the peak amplitude in the two frequency regionscan indicate emotional stress content after much analysis for theindividual subjects. To accent the emotional stress content and providea quantitative information thereof irrespective of the subject, thepresent invention stores a peak amplitude ratio from the subject andcompares it with subsequent peak amplitude ratios in a second ratiocircuit. The second ratio provides a normalization of the peak amplituderatios. The stored ratio may be updated at the discretion of theinterrogator or done automatically at periodic intervals.

OBJECTS OF THE INVENTION It is an object of the present invention toprovide a means for detecting a stressful or emotional condition in ahuman being who is speaking.

An additional object of this invention is to detect this emotional orstressful condition while the person who is speaking is under direct andskillful interrogation.

A further object of this invention is to provide means whereby a validTruth/Lie decision can be rendered by direct observations of the datareadout of a voice or speech analysis system.

A still further object of this invention is to detect the emotional orstressful condition by analysis of the maximum signal amplitude in twoor more frequency regions of a human voice.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawmgs.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an oscillograph of a male voiceresponding with the word yes" in the English language in answer to adirect question in a bandwidth of Ski-I2;

FIG. 2 is an oscillograph of a male voice responding with the word no inthe English language in answer to a direct question in a bandwidth ofSkI-Iz;

FIGS. 3a and 3b are oscillographs of a male voice responding yes in theEnglish language as measured in the l50-300Hz frequency region and600-1200Hz regions, respectively;

FIGS. 4a and 4b are oscillographs of a male voice responding no in theEnglish language as measured in the l50-300I-Iz frequency region and600-1200I-Iz re gions, respectively;

FIG. 5 is a simplified block diagram of a functional embodiment of theinvention;

FIG. 6 is a detailed schematic of the preferred embodiment of theinvention;

FIG. 7 is the plot of the results of a statistical analysis of measuredratio values versus the probability of accurate assessment of the givenemotional state;

FIG. 8 is the plot of the results of a statistical analysis of measuredand normalized ratio values versus the probability of correct assessmentof a given emotional state.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows an oscillograph of amale voice responding with the word yes in the English language inanswer to a direct question at a bandwidth of 5kHz. The wave formcontains two distinct envelopes, the first being for the voiced ye soundand the second being for the voiceless 5 sound. Since the first envelopeof the yes signal wave form is a voiced sound being produced primarilyby the vocal cords and conus elasticus, this envelope will be processedto detect emotional stress content or modulations. The male voiceresponding with the word no" in the English language in a bandwidth ofSkHz is shown in FIG. 2. This response has a single envelope which willbe analyzed by the present device to detect the presence of "finestructure i.e. the rapid modulation of the phonation constituent of thespeech signal.

FIGS. 3a, 3b, 4a and 4b show oscillographs of the same male voice as inFIGS. 1 and 2 responding yes and no, respectively, in the Englishlanguage as measured in the 150-300 Hz and 600-1200Hz frequency regions.The electrical speech signal in each of these bands of frequencies iswell defined. Thus when this energy is rectified and smoothed, signaloutputs are provided whose maximum amplitudes may be readily andaccurately determined.

A simplified block diagram of the present embodiment of the invention isdepicted in FIG. 5. A transducer 2, a microphone in this case, is usedto convert the acoustic utterances or phonation of the subject beinginterrogated to an electrical signal. The electrical signals from themicrophone 2 must have adequate fidelity to tranduce the basic pitchfrequency of the voice about I-Iz for male subjects and 250l-Iz forfemale. The voltage output of the microphone 2 is directed into twoparallel channels, each having an isolation amplifiers 8 and 10 byshielded cables 4 and 6, respectively. The amplified signals are splitinto separate frequency regions by the employment of separate band-passfilters l2 and 14. In the particular embodiment, amplifier 8 feeds thefull voice bandwidth to band-pass filter 12 which separates out a singlefrequency region. This region might occupy any portion of the audiospectrum but in a typical example it could occupy the fundamental pitchregion from I00 to 200 Hz or to 300I-Iz. After the speech energy isfiltered it must be rendered single-valued. A rectifier 16 is a commonmethod to do this. The rectifier 16 in this case selects only positive(or negative) values of the filtered speech energy. Full wave rectifierscould be employed, at the additional circuit complexity involvement.Following rectification, a low pass filter is employed to smooth out thepeak fluctuations of the voice energy. In common use, this filter isvariable so that the correct amount of filtering may be obtained for theparticular voice in question. The output of the low pass filter 20 iscommonly termed the speech envelope. A peak detector and hold circuit 24stores the peak energy value of the filtered speech envelope. The outputof the peak detector and hold circuit 24 is then directed to input port28 of the ratio determining means 32.

Another channel from the microphone is directed through a different passband region at input connection 6 into amplifier l0 and band-pass filter14. This bandpass filter is set to pass a different frequency regionthan the band-pass filter 12. In general, this region will most likelybe a higher frequency region than the first, for example, from 600-1200Hz or thereabouts. As in the other channel, the speech energy is singlevalued by rectifier 18 which must be identical to the rectienvelope inthis particular frequency region. The output of the circuit 26 isdirected to input port 30 of the ratio taking circuit 32, which performsthe arithmetic computation of dividing the peak envelope energy of onechannel by the other.

The output of circuit 32 is separated into two equal value signals. Thefirst signal forms the input to a long time constant storage circuit 38which holds the received signal value until it is deliberatelydischarged or reset by the closing of switch means 40. The switch may becontrolled manually or automatically by control means 42. The signal isreceived by storage circuit 38 when switch means 34 is closed eithermanually or automatically by control means 36. The second portion of thesignal from circuit 32 is received at the numerator port of a dividingor ratio taking circuit 44. This circuit is of the same type as theprevious ratio taking circuit 32. The long term stored signal at theoutput of the storage device 38 is used as the denominator of the secondratio taking circuit 44. The second ratio taking circuit normalizes thesignals from the first ratio taking circuit. The output of circuit 46 isdirected to a volt meter 48 which reads the value of the ratio for eachutterance of the subject and to the analog recorder 50 which recordsthis value for subsequent analysis and comparison.

FIG. 6 is adetailed block schematic of the preferred embodiment of theinvention. A detailed discussion of the components and functioningthereof will further serve to explain the behavior and the functioningof the invention.

A microphone 60 is shown as the acoustic/electric transducer whichtransfers the acoustic energy of the human voice into an electricalsignal. The microphone used in this manner is perfectly typical exceptthat the frequency response of the unit: must cover the fre-' quencyregions of the follow-on filter circuits. Switch means 66 is shown whichmay be used to alternately select the sonic signal from the microphone60 or from a combination of another microphone and a conventional taperecorder 64. The behavior of this second combination of microphone andtape recorder must retain the fidelity of the microphone 60. Namely theunits must pass the entire frequency region that allows operation of thesystem.

The switch means 66 is followed by two operational amplifiers 72 and 134used for isolation purposes. One operational amplifier 72, and its gaindetermining resistors 68 and 70, feeds speech energy to one channel ofthe instrument. The other operational amplifier 134, with its gaindetermining resistors 130 and 132, feeds the second channel of theinstrument.

The first channel of the instrument feeds the amplified signal atterminal 74 to a band-pass filter 76. From the broad-band speech energywhich the enters theband-pass filter 76 only the region from l50-300Hzis allowed to pass through. This region might change depending upon thevoice involved. FIGS. 1 and 2 show the waveforms of a male human voiceresponding with the word yes"and the word no" in the frequency re gionfrom 100Hz through SOOOI-Iz. FIGS. 3 and 4 show the waveforms of thesame voice after passing through the filters 76 and 138. Filter 76passes the spectral region from 150-300Hz and filter 138 passes theregion from 600-l200Hz.

Another stage of isolation employing operational amplifiers follows bothof the band pass filters. The bandpass filter 76 is followed byoperational amplifier 84 with its gain determining resistors and 82. Thebandpass filter 138 is followed by operational amplifier 146, with itsgain determining resistors 142 and 144.

In the preferred embodiment of the invention, the conversion of the dualpolarity signals out of each of the isolation amplifiers is renderedsingle valued or rectified by simple solid state diodes 86 and 148.Reversed polarity diodes are also shown as items 88 and 150. Thispolarity would allow the instrument to function equally as well. Ifdiodes with a particular characteristic were employed, such as a squarelaw characteristic, the instrument would function upon the measure ofspeech energy, i.e. power, in the two band-pass regions. In the presentdevice, there is no statistical difference in the behavior of theinstrument with a true powercharacteristic in the diodes or with astraight rectification process. In the practical case therefor, a pairof simple diodes have been found to suffice. I

In both the low frequency channel and the high frequency channel, thisrectification process takes place in the manner described and the bothchannels are directed again into two operational amplifiers for thepurpose of circuit isolation. In the low frequency channel, theoperational amplifier 94 with its gain determining resistors 90 and 92perform this function. In the high frequency channel, operationalamplifier 156 with its gain determining resistors 152 and 154 islikewise employed. In the low frequency channel, the signal outputappears at point'96 and it passes into a low pass filter networkconsisting of a variable resistor 98 and a fixed capacitor 100. It canbe seen that other types of low pass filters could be employed here toremove the high frequency fluctuations appearing at point 96 andrendering the output of the filter essentially that of the envelope ofthe speech signal, in the defined pass band. The exact time constant ofthis filter is adjusted depending upon the pitch of the voice underassessment. This envelope of signal energy then passes into a peakdetect and hold circuit 102. Such circuits can be readily fabricatedfrom a variety of components and modules by those skilled in the art. Asingle module named Infinite Sample Hold which is manufactured by HybridSystems Corp. can be used. This particularv module has the advantage ofnon-decay of the peak value until the circuit is reset. The output peakvalue appears at point 104 while the reset signal is applied at point106. The peak value is isolated from the followon circuit by anotheroperational amplifier 112, with its gain determining resistors 108 and110. The output at 114 of amplifier 112 appears as the denominator of ananalog division circuit 116. Again, there are many ways that the ratioof two voltages could be taken. Two voltages could be read on two voltmeters and the ratio determined arithmetically. The two voltages couldalso be recorded and the recorded values read from a chart and the ratiodetermined arithmetically. Preferably a modern analog computer modulesuch as Model 107C,

7 manufactured by Hybrid Systems Corp. could be used.

In the high frequency channel, the circuitry is quite the same. Thesignal energy appears at the output of the isolation amplifier 156 atpoint 158 and passes into a similar R/C filter network, where the highfrequency components of the speech envelope in the high frequency regionare filtered out. The value of the time constant which consists ofvariable resistor 160 and fixed capacitor 162 is different from that inthe low frequency channel, since the frequency is quite different.

Again, the signal passes out of the filter into a peak and detector andhold module 166. Under control of the reset signal at port 164 andproviding output at port 168, the peak detector and hold module acts todetect and store the peak signal envelope value that occurred during thephonaton of the subject in the selected frequency region. An isolationamplifier 174, with its gain determining resistors 170 and 172 providesthe high frequency channel peak signal level to the analog divisionmodule as the numerator of the ratio expression. The quotient appears atport 192 where it divides into two equisignal paths. One path travels toswitch means 184 which is under the control of control means 190. Theother path travels to a second analog division circuit or ratio circuit178 which is identical to circuit 116 and appears at the numerator portof the analog ratio taking circuit 178.

The switch means 184 connects the analog ratio of the two frequencies at192 to a long term sample hold storage means 180. When switch means 184is closed by control means 190, the long term storage means will keepholding the peak ratio appearing at 192 until it is reset by resetswitch means 186, also under control of control means 190. This circuitthen feeds this stored value for a selected utterance of the speakerinto the ratio taking circuit 178 on the denominator buss 182. Thus themachine may be calibrated or normalized for a particular speaker, withthe result that his other variations in subsequent utterances will behighly significant. The reset switch 186 operated by control means 190will not be reset until a new subject is being interrogated or until theanalyst desires to update the normalization. The output of this ratiotaking circuit 178 enters switch means 183 which is also operated bycontrol means 190. When a suitable normalizing denominator has been heldor stored and entered into the final ratio taking circuit 178, theratios formed for all subsequent utterances will pass to the indicators.The indicators consist of DC volt meter 108 and recording means 120. Therecording means functions only for the second and all subsequentutterances of the subject since the control means 190 closes switch 183after the first utterance. The control means 190 also provides switchingsignals to peak detect and hold module 102 and 166 as required. It alsoswitches to signals into ans out of the long term storage 180, the finalratio taking circuit 178 and it operates the recorder 120.

FIG. 7 is the plot of the statistical analysis of the ratio valuesobtained from a number of stressful and nonstressful utterances of anumber of different speakers. The plot shows the probability ofcorrectly identifying an utterance as stressful or non-stressful as afunction of the ratio value of that utterance. The plot indicates thatwhen either low or high ratio values occur, the utterance can beassessed to be non-stressful. There is no ratio value range in which anutterance can be assessed, with any confidence, i.e. greater than 50percent, as being stressful.

On the other hand, FIG. 8 is a plot of an analysis of the data takenfrom the preferred embodiment using a normalizing circuit. This data hasbeen normalized by assessment of a specific utterance of the subject.All subsequent utterances of the same subject are then normalized withthis information. it can be seen that normalized ratio values less thanabout 0.59 are stressful and ratio values higher in value arenon-stressful. To obtain a confidence band of greater than percent, theratio values may be set as less than 0.46 for stressful and greater than0.65 for nonstressful. With this circuit behavior it is quite apparentto those skilled in the art that a set of limit lights 200 may beapplied. For example, a red light could activate for an establishedlower limit indicating stress or an untruthful response, an amber lightcould indicate indecision or no opinion in the middle range of the ratiovalues, and a green light could indicate non-stress or a truthfulresponse. When the measured normalized ratio value was higher than agiven amount, the lights may be controlled by level responsive switchessuch as relays or transistors or a combination thereof.

With the above description, any person skilled in the art could discernthe proper functioning of the invention described here. Statistical datataken with the present instrument has demonstrated that conditions ofemotional stress and in particular the Truth/Lie decision can beanalyzed and correctly discerned with a high degree of confidence.Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample only and is not to be taken by way of limitation, the spirit andscope of the invention being limited only by the terms of the appendedclaims.

What is claimed is:

l. A method for detecting emotional stress in the utterance of anindividual comprising:

converting said utterance to an electrical signal;

selecting two different frequency bands of said electrical signal;

detecting and holding the peak amplitude of each frequency band for theduration of the utterance; computing the ratio of the held peakamplitude of one frequency band with the other;

storing a previously computed ratio of said peak amplitudes;

comparing subsequent ratios with said stored ratios;

and displaying the compared results which would be indicative ofemotional stress.

2. A method as in claim 1 wherein selecting comprises amplifying,band-pass filtering, rectifying and smoothing wherein said band-passfiltering and smoothing is different for each selected frequency band.

3. A method as in claim 1 wherein displaying comprises indicatingquantitatively stress, non-stress and indecision.

4. A device for indicating emotional stress from the utterances of ahuman comprising:

means for converting said utterances into electrical signals;

first channel means connected to said converting means for detecting andholding a peak amplitude in a first frequency band for the duration ofthe utterance;

second channel means connected to said converting means for detectingand holding a peak amplitude in a second frequency band for the durationof the utterance;

first ratio means connected to said first and second channel means fortaking the ratio of said detected and held peak amplitudes meansconnected to said first ratio means for storing a previous ratio takenby said first ratio means second ratio means connected to said firstratio means and said storing means for taking the ratio of said storedratio and subsequent detected peak amplitude ratiosj and means connectedto said second ratio means to display said second ratio.

5. A device as in claim 4, said first and second channel means eachincluding:

means for passing electrical signals in a selected frequency band;

means connected to said passing means for rectifying said passed signal;

means connected to said rectifying means for smoothing said rectifiedsignal; and

means connected to said smoothing means for detecting and holding thepeak amplitude of said smoothed signal.

6. A device as in claim 5 wherein said first channel passes a frequencyof -300Hz and said second channel passes a frequency of 600-l200l-lz.

7. A device as in claim 4 wherein said display means comprises threeindicators each responsive to a select region of second ratio valuesthereby indicating stress, non-stress and indecision in the utterance.

8. A device as in claim 4 wherein said first channels frequency band isof a lower frequency than said second channels frequency band, andwherein said first channels detected peak amplitude comprises thedenominator of said first ratio means.

9. A device as in claim 4 wherein said stored ratio comprises thedenominator of said second ratio means and said subsequent peakamplitude ratios comprises the numerators of said second ratio means.

1. A method for detecting emotional stress in the utterance of an individual comprising: converting said utterance to an electrical signal; selecting two different frequency bands of said electrical signal; detecting and holding the peak amplitude of each frequency band for the duration of the utterance; computinG the ratio of the held peak amplitude of one frequency band with the other; storing a previously computed ratio of said peak amplitudes; comparing subsequent ratios with said stored ratios; and displaying the compared results which would be indicative of emotional stress.
 2. A method as in claim 1 wherein selecting comprises amplifying, band-pass filtering, rectifying and smoothing wherein said band-pass filtering and smoothing is different for each selected frequency band.
 3. A method as in claim 1 wherein displaying comprises indicating quantitatively stress, non-stress and indecision.
 4. A device for indicating emotional stress from the utterances of a human comprising: means for converting said utterances into electrical signals; first channel means connected to said converting means for detecting and holding a peak amplitude in a first frequency band for the duration of the utterance; second channel means connected to said converting means for detecting and holding a peak amplitude in a second frequency band for the duration of the utterance; first ratio means connected to said first and second channel means for taking the ratio of said detected and held peak amplitudes means connected to said first ratio means for storing a previous ratio taken by said first ratio means second ratio means connected to said first ratio means and said storing means for taking the ratio of said stored ratio and subsequent detected peak amplitude ratios; and means connected to said second ratio means to display said second ratio.
 5. A device as in claim 4, said first and second channel means each including: means for passing electrical signals in a selected frequency band; means connected to said passing means for rectifying said passed signal; means connected to said rectifying means for smoothing said rectified signal; and means connected to said smoothing means for detecting and holding the peak amplitude of said smoothed signal.
 6. A device as in claim 5 wherein said first channel passes a frequency of 150-300Hz and said second channel passes a frequency of 600-1200Hz.
 7. A device as in claim 4 wherein said display means comprises three indicators each responsive to a select region of second ratio values thereby indicating stress, non-stress and indecision in the utterance.
 8. A device as in claim 4 wherein said first channel''s frequency band is of a lower frequency than said second channel''s frequency band, and wherein said first channel''s detected peak amplitude comprises the denominator of said first ratio means.
 9. A device as in claim 4 wherein said stored ratio comprises the denominator of said second ratio means and said subsequent peak amplitude ratios comprises the numerators of said second ratio means. 